A healthy weight for a woman prior to pregnancy is defined as a BMI of 18.5 to 24.9.Low weight births are
less than 2,500 grams.Very low weight births are less than 1,500 grams.Very preterm births are infants born prior to 32 completed weeks of gestation.Late preterm births are infants born between 34 to 36 completed weeks of gestation.Preterm births are infants born prior to 37 completed weeks of gestation.Singleton birth is a single birth delivery.Low-risk Cesarean births are singleton, full-term (37 weeks gestation or older), with vertex presentation that were delivered using a C-section.Male/female ratio is the number of male resident live births divided by the female resident
live births × 100.
Mothers who smoked while pregnant where those who had a history of smoking, but never quit, plus those who quit at some point between estimated conception and birth date.
Weight gain is considered low or excessive if it falls below or above the IOM recommended range of weight gain. See "Weight Gain During Pregnancy: Reexamining the Guidelines" for details.